Technical Abstract:
Many temperate plants develop a greater ability to withstand freezing after a prior exposure to low but non-freezing temperatures through a complex adaptive process of cold acclimation. Although many changes in gene expression, metabolic processes, and morphology occur during cold acclimation, little is known about the processes that are critical for the development of freezing tolerance. To help understand these processes, we have isolated a series of Arabidopsis mutants that are constitutively freezing tolerant in the absence of cold acclimation. A previously published a mutant, eskimo1, displays increased freezing tolerance, high levels of free proline, but normal regulation of COR genes. We report here the characterization of a new mutant, eskimo2. Two independent alleles of eskimo2 were isolated; both showed increased freezing tolerance without cold acclimation and increased levels of free proline. These results indicate that proline play an important role in the development of freezing tolerance during cold acclimation.